Media loading trays in imaging devices, such as printers and photocopiers, generally have the capacity to load and accommodate media of different sizes. The media loading trays within such devices are well equipped to automatically detect the size of media loaded into the tray. Automatic detection of media size helps prevent certain types of errors, such as, printing on the wrong size, or at a wrong location over the loaded media. To detect the size of the media loaded in the loading tray, one or more movable guides are incorporated within such trays, and a user slides the movable guides to align with the edges of the loaded media.
Conventionally, in many imaging devices, the movable guides are attached to a rack and pinion mechanism. Specifically, the rack is operatively connected to the guide, and transmits the linear motion in response to the movement of the guide. In response to rack's movement, the pinion rotates either clockwise or counter-clockwise, depending on the sense of movement of the guides. A mechanism is connected to the pinion, which detects the degree of rotation of the pinion. The mechanism has a sensor array which generates a signal corresponding to the degrees of rotation of the pinion. Further, the sensor is configured to send a signal to a processing unit. The processing unit converts that signal into a value representing the distance traversed by the movable guides, which facilitates detection of the size of the media loaded into the media loading tray. Eventually, the detected media size is displayed on a user interface of the imaging device.
Among the other conventional approaches, some imaging devices detect the media size automatically, by using two linear sensors, generally. Such linear sensors typically have pins capable of sliding within them, along their lengths. One of the sensors is associated with a movable guide positioned along the length of the loaded media, and the other is associated with a guide positioned along the width of the media. These sensors, being coupled to a rack, are capable of measuring the dimensions (i.e., length and width) of media, using the distance traversed by the guides. Specifically, the rack is directly attached to the guides, and connected to a pinion, to affect rotary motion of the pinion in response to linear movement of the racks, when the guides are moved to align along the edges of the loaded media. The pins within the sensors, being connected to the pinion, slide therein, in response to pinion's rotation. However, the linear sensors incorporated in such conventional mechanism, can measure distances only up to 30 to 40 mm. Alternatively, a linkage mechanism may be positioned between the rack and the sensors, to generate signals corresponding to the media size. The linkage mechanism may be a spring, for example. As the user adjusts the guides to align with the media, the rack move linearly. The rack pushes the link mechanism, which causes the pin to side within the sensor. Eventually, the sensor transmits a signal based on the extent of movement of the pin. The signal is processed by a processing unit, which generates a value representing the size of the loaded media.
However, such conventional systems are costly, need collaboration of many components, and can reduce reliability. Additionally, some automatic media sensing systems may have difficulty distinguishing between loaded media having different dimensions.
Therefore, considering the problems mentioned above, a need exists for an effective mechanism within an imaging device, which can automatically detect the size of the loaded media, precisely, and be more reliable, compared to conventional imaging devices.